How setting the TZ environment variable avoids thousands of system calls
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How setting the TZ environment variable avoids thousands of system calls
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Re: How setting the TZ environment variable avoids thousands of system calls
#2Good blog post explaining the behavior of glibc, I also saw this first hand when profiling Apache awhile back too:
http://mail-archives.apache.org/mod_mbox/httpd-dev/201111.mb...
https://github.com/apache/httpd/blob/trunk/server/util_time....
The internals of glibc can often be pretty surprising sometimes, I'd really encourage people to go spelunking into the glibc source when they are profiling applications.
Re: How setting the TZ environment variable avoids thousands of system calls
#3does anyone know if this impacts docker images as well ?
Re: How setting the TZ environment variable avoids thousands of system calls
#4does anyone know if this impacts docker images as well ?
I would be surprised if this doesn't. There's nothing specific about docker when running this C code from any other processes running on a Linux host.
Re: How setting the TZ environment variable avoids thousands of system calls
#5does anyone know if this impacts docker images as well ?
If you havn't set the TZ variable in the image, then yes.
Re: How setting the TZ environment variable avoids thousands of system calls
#6does anyone know if this impacts docker images as well ?
Yes, at least the Docker images that use glibc as their libc. (eg, most Debian/Ubuntu images)
It looks like musl, which is used on Alpine Linux images for example, will only read it once, and then cache it:
https://github.com/esmil/musl/blob/master/src/time/__tz.c#L1...
It has a mutex/lock around the use of the TZ info, but avoids re-stat'ing the localtime file.
Re: How setting the TZ environment variable avoids thousands of system calls
#7Side note - why do some sites completely hide information about who is behind them? I couldn't find a single thing about that on their blog or main site.
Re: How setting the TZ environment variable avoids thousands of system calls
#8If this has a real-world/measurable/etc. impact why isn't this set by default? Are there potential side-effects? Is it set in some distros but not others?
Re: How setting the TZ environment variable avoids thousands of system calls
#9Side note - why do some sites completely hide information about who is behind them? I couldn't find a single thing about that on their blog or main site.
Maybe it's just that I use packagecloud and follow people in their circle on Twitter, but Joe Damato is the CEO and founder: https://twitter.com/joedamato
I'm under the impression that he may also write a lot these himself? Not entirely certain, though.
Re: How setting the TZ environment variable avoids thousands of system calls
#10Side note - why do some sites completely hide information about who is behind them? I couldn't find a single thing about that on their blog or main site.
All the links are in the footer of the page.